AN ELECTRON-DIFFRACTION INVESTIGATION OF THE DIFFUSE OMEGA-STRUCTURE IN QUENCHED TI-3D TRANSITION-METAL ALLOYS

Diffuse scattering resembling diffraction from the omega phase is investigated in quenched b.c.c. (beta) Ti-Cr using electron diffraction. A new structural model is presented which can reproduce the large shifts of diffuse peaks from the positions of omega-phase Bragg reflections which are seen in this system. Using the model it is proposed that CSRO in conjunction with an atomic size difference are responsible for the occurrence of this structure in quenched beta Ti-3d metal alloys. Evidence is presented for an electronic origin for CSRO in these systems.